It is well known in the electronics industry that the cooling of complementary metal oxide semiconductor (COMOS) integrated circuit devices can substantially enhance the efficiently and speed at which such devices can operate. Such cooling is particularly benificial in the case of CPUs that form the heart of modern day computers. In some cases, it has been found that the clock speed at which a CPU processes programming instructions can increased nearly 300% by cooling the CPU to a temperature of approximately -200.degree. C.
To take advantage of the greatly increased processing speeds achievable with cooled CPUs, a variety of methods and devices have been developed for cooling CPUs and, for that matter, other integrated circuit devices, to below ambient temperatures. One such device comprises a hollow cold plate, which is thermally coupled to a CPU or other integrated circuit device to be cooled. A coolant is circulated from a refrigeration unit through connecting conduits to the cold plate to effectuate cooling of plate and, in turn, of the integrated circuit device. Other known cooling methods include immersion of a CPU module in a coolant such as liquid nitrogen, or interfacing the CPU module with a peltier TEC (thermal electric cooling) device.
One example of an apparatus for cooling an integrated circuit device is disclosed in U.S. Pat. No. 5,574,627 of Porter. In the Porter apparatus, a CPU is mounted in a socket within a sealed insulated chamber. A cryrogenically cooled cold plate is disposed atop and in contact with the CPU within the insulated chamber. The socket pins of the socket project out of the chamber for being soldered or otherwise electrically coupled to the mother board of a computer for electronically coupling the CPU within the sealed chamber to other components of the computer. In use, the CPU is cooled to a desired below ambient temperature by circulating an appropriate refrigerant through the cold plate.
While the apparatus disclosed in Porter functions well to cool a CPU, it nevertheless exhibits certain problems and shortcomings inherent in its design. For example, in column 4, beginning at line 19, it is recognized by Porter that the chilling of the CPU within the sealed chamber also chills the socket pins within the chamber. As a result, the protruding exposed ends of the socket pins, which project out of the chamber and are mounted to the mother board, are also chilled through thermal conduction from the interior of the sealed chamber. The resulting problem is that when the temperature of the exposed ends of the socket pins falls below the local dew point, moisture begins to condense on the exposed pins and on surrounding elements of the mother board. Such condensation is highly undesirable because it can cause temporary or permanent damage to electrical components within a computer in which the cooling system is employed.
In order the address the problem of condensation caused by conductive chilling of these exposed metal pins, Porter teaches that a sealed insulator be mounted to the bottom of the mother board covering the exposed chilled socket pins and isolating them from ambiance. However, this is not a complete solution to the condensation problem for a variety of reasons. First, the interior of the lower insulator in which the pins are housed still contains air with some humidity and some dew point. Accordingly, moisture can still form on the pins enclosed within the lower insulator. This moisture can degrade the electrical connections of the pins to the mother board and, over time, can lead to failure of the circuit. In addition, the solution proposed by Porter requires that additional bulk be added to the back of the circuit board, which is undesirable because space is a premium within modern computers, and also requires that a seal of high integrity be formed and maintained between the lower insulator and the bottom of the mother board. Further, the outer surface of the cooling chamber on top of the mother board must also be sealed to the mother board to prevent ambient air from entering the space between the cooling chamber and the surface of the mother board, to prevent condensation on the exposed portions of the pins in this region. Since it is very difficult to maintain the integrity of such seals for long periods of time, ambient air can still seep into the regions around the chilled pins and condensation can still occur. Thus, Porter's solution to the problem of condensation is incomplete and is also inefficient because it calls for additional components and installation steps.
Accordingly, there exists a need for a reliable, efficient, and economical method and apparatus for chilling integrated circuit devices such as computer CPUs to below ambient temperatures while at the same time preventing the formation of condensation on connector pins or other exposed elements of the cooling apparatus. Preferably, this should be accomplished without requiring any special treatment of the mother board and without requiring installation of auxiliary insulating chambers or other ancillary elements, but such is not a limitation of the invention. It is to the provision of such an apparatus that the present invention is primarily directed.